Hybrid Simulations of Interstellar Pickup Ions at the Solar Wind Termination Shock Revisited
We revisit previous hybrid simulations of the heating and acceleration of interstellar pickup ions (PUIs) at the solar wind termination shock. In previous simulations, a relatively cold initial distribution of PUIs was assumed; and while the resulting shock-heated distribution was consistent with Vo...
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2025-01-01
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| Online Access: | https://doi.org/10.3847/1538-4357/ada89c |
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| author | Joe Giacalone M. Kornbleuth M. Opher M. Gkioulidou J. Köta E. Puzzoni J. D. Richardson G. P. Zank |
| author_facet | Joe Giacalone M. Kornbleuth M. Opher M. Gkioulidou J. Köta E. Puzzoni J. D. Richardson G. P. Zank |
| author_sort | Joe Giacalone |
| collection | DOAJ |
| description | We revisit previous hybrid simulations of the heating and acceleration of interstellar pickup ions (PUIs) at the solar wind termination shock. In previous simulations, a relatively cold initial distribution of PUIs was assumed; and while the resulting shock-heated distribution was consistent with Voyager 2 LECP measurements at about 30 keV, the intensity of the distribution downstream of the shock in the ~1–10 keV energy range was lower than predictions based on analysis of energetic neutral atoms (ENAs) from the Interstellar Boundary Explorer-Hi and Cassini's Ion and Neutral Camera. Here we perform new simulations with more realistic initial PUI distributions. We assume the distribution is a partially filled spherical shell in velocity space with a radius that varies from 320 to 640 km s ^−1 . We then use the distributions downstream of the shock from these new simulations to estimate the ENA flux spectrum and compare with observations. We find that the predicted ENA spectrum from the new simulations much better matches the observations over a broad range of energies. We conclude that the hybrid simulations provide reasonable predictions for the distribution of charged particles in the energy range from ~0.5 to 50 keV. |
| format | Article |
| id | doaj-art-52a062afab7a4d01a9ae0f51d38e08a5 |
| institution | Kabale University |
| issn | 1538-4357 |
| language | English |
| publishDate | 2025-01-01 |
| publisher | IOP Publishing |
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| series | The Astrophysical Journal |
| spelling | doaj-art-52a062afab7a4d01a9ae0f51d38e08a52025-02-03T10:10:06ZengIOP PublishingThe Astrophysical Journal1538-43572025-01-0198012910.3847/1538-4357/ada89cHybrid Simulations of Interstellar Pickup Ions at the Solar Wind Termination Shock RevisitedJoe Giacalone0https://orcid.org/0000-0002-0850-4233M. Kornbleuth1https://orcid.org/0000-0002-3479-1766M. Opher2https://orcid.org/0000-0002-8767-8273M. Gkioulidou3J. Köta4E. Puzzoni5https://orcid.org/0009-0009-5314-348XJ. D. Richardson6https://orcid.org/0000-0003-4041-7540G. P. Zank7https://orcid.org/0000-0002-4642-6192Lunar & Planetary Laboratory, University of Arizona , Tucson, AZ 85721, USA ; giacalon@lpl.arizona.eduAstronomy Department, Boston University , Boston, MA 02215, USAAstronomy Department, Boston University , Boston, MA 02215, USAApplied Physics Laboratory, Johns Hopkins University , Laurel, MD 20723, USALunar & Planetary Laboratory, University of Arizona , Tucson, AZ 85721, USA ; giacalon@lpl.arizona.eduLunar & Planetary Laboratory, University of Arizona , Tucson, AZ 85721, USA ; giacalon@lpl.arizona.eduKavli Institute for Astrophysics and Space Research and Department of Physics , Massachusetts Institute of Technology, Cambridge, MA 02139, USACenter for Space Plasma and Aeronomic Research (CSPAR), University of Alabama in Huntsville , Huntsville, AL 35805, USAWe revisit previous hybrid simulations of the heating and acceleration of interstellar pickup ions (PUIs) at the solar wind termination shock. In previous simulations, a relatively cold initial distribution of PUIs was assumed; and while the resulting shock-heated distribution was consistent with Voyager 2 LECP measurements at about 30 keV, the intensity of the distribution downstream of the shock in the ~1–10 keV energy range was lower than predictions based on analysis of energetic neutral atoms (ENAs) from the Interstellar Boundary Explorer-Hi and Cassini's Ion and Neutral Camera. Here we perform new simulations with more realistic initial PUI distributions. We assume the distribution is a partially filled spherical shell in velocity space with a radius that varies from 320 to 640 km s ^−1 . We then use the distributions downstream of the shock from these new simulations to estimate the ENA flux spectrum and compare with observations. We find that the predicted ENA spectrum from the new simulations much better matches the observations over a broad range of energies. We conclude that the hybrid simulations provide reasonable predictions for the distribution of charged particles in the energy range from ~0.5 to 50 keV.https://doi.org/10.3847/1538-4357/ada89cPickup ionsTermination shockCosmic rays |
| spellingShingle | Joe Giacalone M. Kornbleuth M. Opher M. Gkioulidou J. Köta E. Puzzoni J. D. Richardson G. P. Zank Hybrid Simulations of Interstellar Pickup Ions at the Solar Wind Termination Shock Revisited The Astrophysical Journal Pickup ions Termination shock Cosmic rays |
| title | Hybrid Simulations of Interstellar Pickup Ions at the Solar Wind Termination Shock Revisited |
| title_full | Hybrid Simulations of Interstellar Pickup Ions at the Solar Wind Termination Shock Revisited |
| title_fullStr | Hybrid Simulations of Interstellar Pickup Ions at the Solar Wind Termination Shock Revisited |
| title_full_unstemmed | Hybrid Simulations of Interstellar Pickup Ions at the Solar Wind Termination Shock Revisited |
| title_short | Hybrid Simulations of Interstellar Pickup Ions at the Solar Wind Termination Shock Revisited |
| title_sort | hybrid simulations of interstellar pickup ions at the solar wind termination shock revisited |
| topic | Pickup ions Termination shock Cosmic rays |
| url | https://doi.org/10.3847/1538-4357/ada89c |
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